Wheel hub assemblies support a vehicle wheel on one side and if the wheel is driving, they are angularly connected to a relative constant velocity joint for transmitting the driving torque from the axle shaft to the wheel itself. Wheel hub assemblies have an axis A of rotation and comprise an inner ring and an outer ring coaxial to each other and to axis A of rotation and rotatable with respect to each other by the arrangement of a crown of rolling bodies therebetween.
The inner ring is a flanged inner ring for allowing a wheel to be attached to the assembly and comprises:
a flange crosswise axis A of rotation,
an axle extending along axis A of rotation and made integral with and of the same material as the flange, and
an insert ring, which is axially mounted on the axle on the side opposite to the flange with respect to the axle itself, and is axially locked against a shoulder of the axle by a rolled edge.
The transmission of the driving torque from the constant velocity joint to the wheel hub is ensured by conjugate motion transmission toothed means provided on the adjacent and facing ends of the wheel hub and of the outer ring of the constant velocity joint; the toothed means may consist of a typical splined coupling or a pair of front toothings that couple to each other head to head, as shown in WO2009/140996, in EP2042755, or again in WO2008/006339.
In particular, in the case of provision of front toothings, the junction zone between wheel hub and constant velocity joint must be protected against infiltrations of external contaminants (water, dust, mud, dirt); the same applies to the rolling bodies mounted arranged between the inner ring and the outer ring which is provided with the fixing means to the suspension upright.
Such protection is obtained according to WO2008/006339 by a single sealing assembly made of two opposite shields, a first one fixed onto the inner ring of the bearing, on the side facing the constant velocity joint, and a second one fixed to the outer ring of the bearing and carrying a sealing ring provided with one or more sliding lips which cooperate in contact with the first shield. The first shield has a complex shape obtained by a dual fold, so that a sleeve portion thereof extends so as to protrude from the inner ring of the bearing and towards the outer ring of the constant velocity joint, covering the junction zone. This protruding portion may be provided, at least at the free end thereof, with an annular seal which frontally cooperates with the outer ring of the constant velocity joint; moreover, the protruding portion or the face of a flange portion of the first shield, facing in use the constant velocity joint, may be provided with an annular signal generating element (also called “phonic wheel”) consisting, if the shield is made of a ferromagnetic metal material, of an alternation of projections and depressions, or of an annular sealing portion made of a magnetizable elastomeric material, magnetized so as to have an alternation of magnetized and non-magnetized zones, or of zones having opposite polarities. Once in use coupled with a suitable sensor, the rotation of the “phonic wheel”, which according to what said is integral with the inner bearing ring, generates a signal that serves for detecting the rotation speed of the vehicle wheel.
The solution according to WO2008/006339 is expensive, complex to manufacture and produces large overall dimensions, both in radial and in axial directions.
In the case of WO2009/140996, the first shield has a simple L-shape in radial section and carries the signal generating element on the flange portion thereof; the protection of the junction zone is carried out by a second sealing assembly, separate from and adjacent to the sealing assembly arranged to protect the rolling bodies, mounted fitted, through a tubular core thereof, onto the outer lateral surface of the inner bearing ring; at the free end thereof, the tubular core carries an annular sleeve seal which makes a radial seal on the outer ring of the joint. This solution greatly increases the axial dimensions of the bearing since the inner ring of the same must be made adequately long for allowing the separate fitting of both sealing assemblies. Moreover, in order to obtain the fitting of the second sealing assembly it is preferable to have a shoulder available to the same whereon the thrust required in the mounting step is exerted. This should be obtained on the core towards the zone of the free end thereof, at the end of the fitting zone on the inner ring which is therefore subject to peak load in the mounting step and may easily get deformed.
The object of the present invention is to provide a static sealing device for wheel hub assemblies connected to constant velocity joints which is free from the above drawbacks, having low costs and high ease of manufacture, high protection efficiency on the rolling bodies and the coupling zone between joint and wheel hub and reduced axial and radial dimensions.